thodg/libgit2

diff --git a/include/git2/attr.h b/include/git2/attr.h
index a3ab5a7..62c2ed6 100644
--- a/include/git2/attr.h
+++ b/include/git2/attr.h
@@ -130,9 +130,32 @@ GIT_EXTERN(git_attr_value_t) git_attr_value(const char *attr);
  *
  * Passing the `GIT_ATTR_CHECK_INCLUDE_HEAD` flag will use attributes
  * from a `.gitattributes` file in the repository at the HEAD revision.
+ *
+ * Passing the `GIT_ATTR_CHECK_INCLUDE_COMMIT` flag will use attributes
+ * from a `.gitattributes` file in a specific commit.
  */
 #define GIT_ATTR_CHECK_NO_SYSTEM        (1 << 2)
 #define GIT_ATTR_CHECK_INCLUDE_HEAD     (1 << 3)
+#define GIT_ATTR_CHECK_INCLUDE_COMMIT   (1 << 4)
+
+/**
+* An options structure for querying attributes.
+*/
+typedef struct {
+	unsigned int version;
+
+	/** A combination of GIT_ATTR_CHECK flags */
+	unsigned int flags;
+
+	/**
+	 * The commit to load attributes from, when
+	 * `GIT_ATTR_CHECK_INCLUDE_COMMIT` is specified.
+	 */
+	git_oid *commit_id;
+} git_attr_options;
+
+#define GIT_ATTR_OPTIONS_VERSION 1
+#define GIT_ATTR_OPTIONS_INIT {GIT_ATTR_OPTIONS_VERSION}
 
 /**
  * Look up the value of one git attribute for path.
@@ -157,6 +180,28 @@ GIT_EXTERN(int) git_attr_get(
 	const char *name);
 
 /**
+ * Look up the value of one git attribute for path with extended options.
+ *
+ * @param value_out Output of the value of the attribute.  Use the GIT_ATTR_...
+ *             macros to test for TRUE, FALSE, UNSPECIFIED, etc. or just
+ *             use the string value for attributes set to a value.  You
+ *             should NOT modify or free this value.
+ * @param repo The repository containing the path.
+ * @param opts The `git_attr_options` to use when querying these attributes.
+ * @param path The path to check for attributes.  Relative paths are
+ *             interpreted relative to the repo root.  The file does
+ *             not have to exist, but if it does not, then it will be
+ *             treated as a plain file (not a directory).
+ * @param name The name of the attribute to look up.
+ */
+GIT_EXTERN(int) git_attr_get_ext(
+	const char **value_out,
+	git_repository *repo,
+	git_attr_options *opts,
+	const char *path,
+	const char *name);
+
+/**
  * Look up a list of git attributes for path.
  *
  * Use this if you have a known list of attributes that you want to
@@ -194,6 +239,30 @@ GIT_EXTERN(int) git_attr_get_many(
 	const char **names);
 
 /**
+ * Look up a list of git attributes for path with extended options.
+ *
+ * @param values_out An array of num_attr entries that will have string
+ *             pointers written into it for the values of the attributes.
+ *             You should not modify or free the values that are written
+ *             into this array (although of course, you should free the
+ *             array itself if you allocated it).
+ * @param repo The repository containing the path.
+ * @param opts The `git_attr_options` to use when querying these attributes.
+ * @param path The path inside the repo to check attributes.  This
+ *             does not have to exist, but if it does not, then
+ *             it will be treated as a plain file (i.e. not a directory).
+ * @param num_attr The number of attributes being looked up
+ * @param names An array of num_attr strings containing attribute names.
+ */
+GIT_EXTERN(int) git_attr_get_many_ext(
+	const char **values_out,
+	git_repository *repo,
+	git_attr_options *opts,
+	const char *path,
+	size_t num_attr,
+	const char **names);
+
+/**
  * The callback used with git_attr_foreach.
  *
  * This callback will be invoked only once per attribute name, even if there
@@ -232,6 +301,26 @@ GIT_EXTERN(int) git_attr_foreach(
 	void *payload);
 
 /**
+ * Loop over all the git attributes for a path with extended options.
+ *
+ * @param repo The repository containing the path.
+ * @param opts The `git_attr_options` to use when querying these attributes.
+ * @param path Path inside the repo to check attributes.  This does not have
+ *             to exist, but if it does not, then it will be treated as a
+ *             plain file (i.e. not a directory).
+ * @param callback Function to invoke on each attribute name and value.
+ *                 See git_attr_foreach_cb.
+ * @param payload Passed on as extra parameter to callback function.
+ * @return 0 on success, non-zero callback return value, or error code
+ */
+GIT_EXTERN(int) git_attr_foreach_ext(
+	git_repository *repo,
+	git_attr_options *opts,
+	const char *path,
+	git_attr_foreach_cb callback,
+	void *payload);
+
+/**
  * Flush the gitattributes cache.
  *
  * Call this if you have reason to believe that the attributes files on
diff --git a/include/git2/blob.h b/include/git2/blob.h
index 3f67386..fceb5c7 100644
--- a/include/git2/blob.h
+++ b/include/git2/blob.h
@@ -114,6 +114,12 @@ typedef enum {
 	 * in the HEAD commit.
 	 */
 	GIT_BLOB_FILTER_ATTRIBUTES_FROM_HEAD = (1 << 2),
+
+	/**
+	 * When set, filters will be loaded from a `.gitattributes` file
+	 * in the specified commit.
+	 */
+	GIT_BLOB_FILTER_ATTRIBUTES_FROM_COMMIT = (1 << 3),
 } git_blob_filter_flag_t;
 
 /**
@@ -128,6 +134,12 @@ typedef struct {
 
 	/** Flags to control the filtering process, see `git_blob_filter_flag_t` above */
 	uint32_t flags;
+
+	/**
+	 * The commit to load attributes from, when
+	 * `GIT_BLOB_FILTER_ATTRIBUTES_FROM_COMMIT` is specified.
+	 */
+	git_oid *commit_id;
 } git_blob_filter_options;
 
 #define GIT_BLOB_FILTER_OPTIONS_VERSION 1
diff --git a/include/git2/filter.h b/include/git2/filter.h
index a0185ee..044c3b8 100644
--- a/include/git2/filter.h
+++ b/include/git2/filter.h
@@ -49,9 +49,34 @@ typedef enum {
 
 	/** Load attributes from `.gitattributes` in the root of HEAD */
 	GIT_FILTER_ATTRIBUTES_FROM_HEAD = (1u << 2),
+
+	/**
+	 * Load attributes from `.gitattributes` in a given commit.
+	 * This can only be specified in a `git_filter_options`.
+	 */
+	GIT_FILTER_ATTRIBUTES_FROM_COMMIT = (1u << 3),
 } git_filter_flag_t;
 
 /**
+ * Filtering options
+ */
+typedef struct {
+	unsigned int version;
+
+	/** See `git_filter_flag_t` above */
+	uint32_t flags;
+
+	/**
+	 * The commit to load attributes from, when
+	 * `GIT_FILTER_ATTRIBUTES_FROM_COMMIT` is specified.
+	 */
+	git_oid *commit_id;
+} git_filter_options;
+
+ #define GIT_FILTER_OPTIONS_VERSION 1
+ #define GIT_FILTER_OPTIONS_INIT {GIT_FILTER_OPTIONS_VERSION}
+
+/**
  * A filter that can transform file data
  *
  * This represents a filter that can be used to transform or even replace
@@ -104,6 +129,29 @@ GIT_EXTERN(int) git_filter_list_load(
 	uint32_t flags);
 
 /**
+ * Load the filter list for a given path.
+ *
+ * This will return 0 (success) but set the output git_filter_list to NULL
+ * if no filters are requested for the given file.
+ *
+ * @param filters Output newly created git_filter_list (or NULL)
+ * @param repo Repository object that contains `path`
+ * @param blob The blob to which the filter will be applied (if known)
+ * @param path Relative path of the file to be filtered
+ * @param mode Filtering direction (WT->ODB or ODB->WT)
+ * @param opts The `git_filter_options` to use when loading filters
+ * @return 0 on success (which could still return NULL if no filters are
+ *         needed for the requested file), <0 on error
+ */
+GIT_EXTERN(int) git_filter_list_load_ext(
+	git_filter_list **filters,
+	git_repository *repo,
+	git_blob *blob,
+	const char *path,
+	git_filter_mode_t mode,
+	git_filter_options *opts);
+
+/**
  * Query the filter list to see if a given filter (by name) will run.
  * The built-in filters "crlf" and "ident" can be queried, otherwise this
  * is the name of the filter specified by the filter attribute.
diff --git a/src/attr.c b/src/attr.c
index cab5e8b..03b720c 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -36,16 +36,16 @@ git_attr_value_t git_attr_value(const char *attr)
 static int collect_attr_files(
 	git_repository *repo,
 	git_attr_session *attr_session,
-	uint32_t flags,
+	git_attr_options *opts,
 	const char *path,
 	git_vector *files);
 
 static void release_attr_files(git_vector *files);
 
-int git_attr_get(
+int git_attr_get_ext(
 	const char **value,
 	git_repository *repo,
-	uint32_t flags,
+	git_attr_options *opts,
 	const char *pathname,
 	const char *name)
 {
@@ -61,6 +61,7 @@ int git_attr_get(
 	GIT_ASSERT_ARG(value);
 	GIT_ASSERT_ARG(repo);
 	GIT_ASSERT_ARG(name);
+	GIT_ERROR_CHECK_VERSION(opts, GIT_ATTR_OPTIONS_VERSION, "git_attr_options");
 
 	*value = NULL;
 
@@ -70,7 +71,7 @@ int git_attr_get(
 	if (git_attr_path__init(&path, repo, pathname, git_repository_workdir(repo), dir_flag) < 0)
 		return -1;
 
-	if ((error = collect_attr_files(repo, NULL, flags, pathname, &files)) < 0)
+	if ((error = collect_attr_files(repo, NULL, opts, pathname, &files)) < 0)
 		goto cleanup;
 
 	memset(&attr, 0, sizeof(attr));
@@ -97,6 +98,20 @@ cleanup:
 	return error;
 }
 
+int git_attr_get(
+	const char **value,
+	git_repository *repo,
+	uint32_t flags,
+	const char *pathname,
+	const char *name)
+{
+	git_attr_options opts = GIT_ATTR_OPTIONS_INIT;
+
+	opts.flags = flags;
+
+	return git_attr_get_ext(value, repo, &opts, pathname, name);
+}
+
 
 typedef struct {
 	git_attr_name name;
@@ -107,7 +122,7 @@ int git_attr_get_many_with_session(
 	const char **values,
 	git_repository *repo,
 	git_attr_session *attr_session,
-	uint32_t flags,
+	git_attr_options *opts,
 	const char *pathname,
 	size_t num_attr,
 	const char **names)
@@ -129,6 +144,7 @@ int git_attr_get_many_with_session(
 	GIT_ASSERT_ARG(repo);
 	GIT_ASSERT_ARG(pathname);
 	GIT_ASSERT_ARG(names);
+	GIT_ERROR_CHECK_VERSION(opts, GIT_ATTR_OPTIONS_VERSION, "git_attr_options");
 
 	if (git_repository_is_bare(repo))
 		dir_flag = GIT_DIR_FLAG_FALSE;
@@ -136,7 +152,7 @@ int git_attr_get_many_with_session(
 	if (git_attr_path__init(&path, repo, pathname, git_repository_workdir(repo), dir_flag) < 0)
 		return -1;
 
-	if ((error = collect_attr_files(repo, attr_session, flags, pathname, &files)) < 0)
+	if ((error = collect_attr_files(repo, attr_session, opts, pathname, &files)) < 0)
 		goto cleanup;
 
 	info = git__calloc(num_attr, sizeof(attr_get_many_info));
@@ -190,8 +206,24 @@ int git_attr_get_many(
 	size_t num_attr,
 	const char **names)
 {
+	git_attr_options opts = GIT_ATTR_OPTIONS_INIT;
+
+	opts.flags = flags;
+
 	return git_attr_get_many_with_session(
-		values, repo, NULL, flags, pathname, num_attr, names);
+		values, repo, NULL, &opts, pathname, num_attr, names);
+}
+
+int git_attr_get_many_ext(
+	const char **values,
+	git_repository *repo,
+	git_attr_options *opts,
+	const char *pathname,
+	size_t num_attr,
+	const char **names)
+{
+	return git_attr_get_many_with_session(
+		values, repo, NULL, opts, pathname, num_attr, names);
 }
 
 int git_attr_foreach(
@@ -201,6 +233,20 @@ int git_attr_foreach(
 	int (*callback)(const char *name, const char *value, void *payload),
 	void *payload)
 {
+	git_attr_options opts = GIT_ATTR_OPTIONS_INIT;
+
+	opts.flags = flags;
+
+	return git_attr_foreach_ext(repo, &opts, pathname, callback, payload);
+}
+
+int git_attr_foreach_ext(
+	git_repository *repo,
+	git_attr_options *opts,
+	const char *pathname,
+	int (*callback)(const char *name, const char *value, void *payload),
+	void *payload)
+{
 	int error;
 	git_attr_path path;
 	git_vector files = GIT_VECTOR_INIT;
@@ -213,6 +259,7 @@ int git_attr_foreach(
 
 	GIT_ASSERT_ARG(repo);
 	GIT_ASSERT_ARG(callback);
+	GIT_ERROR_CHECK_VERSION(opts, GIT_ATTR_OPTIONS_VERSION, "git_attr_options");
 
 	if (git_repository_is_bare(repo))
 		dir_flag = GIT_DIR_FLAG_FALSE;
@@ -220,7 +267,7 @@ int git_attr_foreach(
 	if (git_attr_path__init(&path, repo, pathname, git_repository_workdir(repo), dir_flag) < 0)
 		return -1;
 
-	if ((error = collect_attr_files(repo, NULL, flags, pathname, &files)) < 0 ||
+	if ((error = collect_attr_files(repo, NULL, opts, pathname, &files)) < 0 ||
 	    (error = git_strmap_new(&seen)) < 0)
 		goto cleanup;
 
@@ -253,26 +300,43 @@ cleanup:
 	return error;
 }
 
-static int preload_attr_file(
+static int preload_attr_source(
 	git_repository *repo,
 	git_attr_session *attr_session,
-	git_attr_file_source source,
-	const char *base,
-	const char *file,
-	bool allow_macros)
+	git_attr_file_source *source)
 {
 	int error;
 	git_attr_file *preload = NULL;
 
-	if (!file)
+	if (!source)
 		return 0;
-	if (!(error = git_attr_cache__get(&preload, repo, attr_session, source, base, file,
-					  git_attr_file__parse_buffer, allow_macros)))
+
+	error = git_attr_cache__get(&preload, repo, attr_session, source,
+	                            git_attr_file__parse_buffer, true);
+
+	if (!error)
 		git_attr_file__free(preload);
 
 	return error;
 }
 
+GIT_INLINE(int) preload_attr_file(
+	git_repository *repo,
+	git_attr_session *attr_session,
+	const char *base,
+	const char *filename)
+{
+	git_attr_file_source source = { GIT_ATTR_FILE_SOURCE_FILE };
+
+	if (!filename)
+		return 0;
+
+	source.base = base;
+	source.filename = filename;
+
+	return preload_attr_source(repo, attr_session, &source);
+}
+
 static int system_attr_file(
 	git_buf *out,
 	git_attr_session *attr_session)
@@ -314,9 +378,12 @@ static int system_attr_file(
 static int attr_setup(
 	git_repository *repo,
 	git_attr_session *attr_session,
-	uint32_t flags)
+	git_attr_options *opts)
 {
-	git_buf path = GIT_BUF_INIT;
+	git_buf system = GIT_BUF_INIT, info = GIT_BUF_INIT;
+	git_attr_file_source index_source = { GIT_ATTR_FILE_SOURCE_INDEX, NULL, GIT_ATTR_FILE, NULL };
+	git_attr_file_source head_source = { GIT_ATTR_FILE_SOURCE_COMMIT, NULL, GIT_ATTR_FILE, NULL };
+	git_attr_file_source commit_source = { GIT_ATTR_FILE_SOURCE_COMMIT, NULL, GIT_ATTR_FILE, NULL };
 	git_index *idx = NULL;
 	const char *workdir;
 	int error = 0;
@@ -332,45 +399,51 @@ static int attr_setup(
 	 * definitions will be available for later file parsing.
 	 */
 
-	if ((error = system_attr_file(&path, attr_session)) < 0 ||
-	    (error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
-				       NULL, path.ptr, true)) < 0) {
+	if ((error = system_attr_file(&system, attr_session)) < 0 ||
+	    (error = preload_attr_file(repo, attr_session, NULL, system.ptr)) < 0) {
 		if (error != GIT_ENOTFOUND)
 			goto out;
+
+		error = 0;
 	}
 
-	if ((error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
-				       NULL, git_repository_attr_cache(repo)->cfg_attr_file, true)) < 0)
+	if ((error = preload_attr_file(repo, attr_session, NULL,
+	                               git_repository_attr_cache(repo)->cfg_attr_file)) < 0)
 		goto out;
 
-	git_buf_clear(&path); /* git_repository_item_path expects an empty buffer, because it uses git_buf_set */
-	if ((error = git_repository_item_path(&path, repo, GIT_REPOSITORY_ITEM_INFO)) < 0 ||
-	    (error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
-				       path.ptr, GIT_ATTR_FILE_INREPO, true)) < 0) {
+	if ((error = git_repository_item_path(&info, repo, GIT_REPOSITORY_ITEM_INFO)) < 0 ||
+	    (error = preload_attr_file(repo, attr_session, info.ptr, GIT_ATTR_FILE_INREPO)) < 0) {
 		if (error != GIT_ENOTFOUND)
 			goto out;
+
+		error = 0;
 	}
 
 	if ((workdir = git_repository_workdir(repo)) != NULL &&
-	    (error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
-				       workdir, GIT_ATTR_FILE, true)) < 0)
+	    (error = preload_attr_file(repo, attr_session, workdir, GIT_ATTR_FILE)) < 0)
 			goto out;
 
 	if ((error = git_repository_index__weakptr(&idx, repo)) < 0 ||
-	    (error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_INDEX,
-				       NULL, GIT_ATTR_FILE, true)) < 0)
+	    (error = preload_attr_source(repo, attr_session, &index_source)) < 0)
 			goto out;
 
-	if ((flags & GIT_ATTR_CHECK_INCLUDE_HEAD) != 0 &&
-	    (error = preload_attr_file(repo, attr_session, GIT_ATTR_FILE__FROM_HEAD,
-				       NULL, GIT_ATTR_FILE, true)) < 0)
+	if ((opts && (opts->flags & GIT_ATTR_CHECK_INCLUDE_HEAD) != 0) &&
+	    (error = preload_attr_source(repo, attr_session, &head_source)) < 0)
 		goto out;
 
+	if ((opts && (opts->flags & GIT_ATTR_CHECK_INCLUDE_COMMIT) != 0)) {
+		commit_source.commit_id = opts->commit_id;
+
+		if ((error = preload_attr_source(repo, attr_session, &commit_source)) < 0)
+			goto out;
+	}
+
 	if (attr_session)
 		attr_session->init_setup = 1;
 
 out:
-	git_buf_dispose(&path);
+	git_buf_dispose(&system);
+	git_buf_dispose(&info);
 
 	return error;
 }
@@ -415,56 +488,60 @@ int git_attr_add_macro(
 typedef struct {
 	git_repository *repo;
 	git_attr_session *attr_session;
-	uint32_t flags;
+	git_attr_options *opts;
 	const char *workdir;
 	git_index *index;
 	git_vector *files;
 } attr_walk_up_info;
 
 static int attr_decide_sources(
-	uint32_t flags, bool has_wd, bool has_index, git_attr_file_source *srcs)
+	uint32_t flags,
+	bool has_wd,
+	bool has_index,
+	git_attr_file_source_t *srcs)
 {
 	int count = 0;
 
 	switch (flags & 0x03) {
 	case GIT_ATTR_CHECK_FILE_THEN_INDEX:
 		if (has_wd)
-			srcs[count++] = GIT_ATTR_FILE__FROM_FILE;
+			srcs[count++] = GIT_ATTR_FILE_SOURCE_FILE;
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE_SOURCE_INDEX;
 		break;
 	case GIT_ATTR_CHECK_INDEX_THEN_FILE:
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE_SOURCE_INDEX;
 		if (has_wd)
-			srcs[count++] = GIT_ATTR_FILE__FROM_FILE;
+			srcs[count++] = GIT_ATTR_FILE_SOURCE_FILE;
 		break;
 	case GIT_ATTR_CHECK_INDEX_ONLY:
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE_SOURCE_INDEX;
 		break;
 	}
 
-	if ((flags & GIT_ATTR_CHECK_INCLUDE_HEAD) != 0)
-		srcs[count++] = GIT_ATTR_FILE__FROM_HEAD;
+	if ((flags & GIT_ATTR_CHECK_INCLUDE_HEAD) != 0 ||
+	    (flags & GIT_ATTR_CHECK_INCLUDE_COMMIT) != 0)
+		srcs[count++] = GIT_ATTR_FILE_SOURCE_COMMIT;
 
 	return count;
 }
 
-static int push_attr_file(
+static int push_attr_source(
 	git_repository *repo,
 	git_attr_session *attr_session,
 	git_vector *list,
-	git_attr_file_source source,
-	const char *base,
-	const char *filename,
+	git_attr_file_source *source,
 	bool allow_macros)
 {
 	int error = 0;
 	git_attr_file *file = NULL;
 
 	error = git_attr_cache__get(&file, repo, attr_session,
-		source, base, filename, git_attr_file__parse_buffer, allow_macros);
+	                            source,
+	                            git_attr_file__parse_buffer,
+	                            allow_macros);
 
 	if (error < 0)
 		return error;
@@ -477,20 +554,40 @@ static int push_attr_file(
 	return error;
 }
 
+GIT_INLINE(int) push_attr_file(
+	git_repository *repo,
+	git_attr_session *attr_session,
+	git_vector *list,
+	const char *base,
+	const char *filename)
+{
+	git_attr_file_source source = { GIT_ATTR_FILE_SOURCE_FILE, base, filename };
+	return push_attr_source(repo, attr_session, list, &source, true);
+}
+
 static int push_one_attr(void *ref, const char *path)
 {
 	attr_walk_up_info *info = (attr_walk_up_info *)ref;
-	git_attr_file_source src[GIT_ATTR_FILE_NUM_SOURCES];
+	git_attr_file_source_t src[GIT_ATTR_FILE_NUM_SOURCES];
 	int error = 0, n_src, i;
 	bool allow_macros;
 
-	n_src = attr_decide_sources(
-		info->flags, info->workdir != NULL, info->index != NULL, src);
+	n_src = attr_decide_sources(info->opts ? info->opts->flags : 0,
+	                            info->workdir != NULL,
+	                            info->index != NULL,
+	                            src);
+
 	allow_macros = info->workdir ? !strcmp(info->workdir, path) : false;
 
-	for (i = 0; !error && i < n_src; ++i)
-		error = push_attr_file(info->repo, info->attr_session, info->files,
-				       src[i], path, GIT_ATTR_FILE, allow_macros);
+	for (i = 0; !error && i < n_src; ++i) {
+		git_attr_file_source source = { src[i], path, GIT_ATTR_FILE };
+
+		if (src[i] == GIT_ATTR_FILE_SOURCE_COMMIT && info->opts)
+			source.commit_id = info->opts->commit_id;
+
+		error = push_attr_source(info->repo, info->attr_session, info->files,
+		                       &source, allow_macros);
+	}
 
 	return error;
 }
@@ -510,7 +607,7 @@ static void release_attr_files(git_vector *files)
 static int collect_attr_files(
 	git_repository *repo,
 	git_attr_session *attr_session,
-	uint32_t flags,
+	git_attr_options *opts,
 	const char *path,
 	git_vector *files)
 {
@@ -519,7 +616,7 @@ static int collect_attr_files(
 	const char *workdir = git_repository_workdir(repo);
 	attr_walk_up_info info = { NULL };
 
-	if ((error = attr_setup(repo, attr_session, flags)) < 0)
+	if ((error = attr_setup(repo, attr_session, opts)) < 0)
 		return error;
 
 	/* Resolve path in a non-bare repo */
@@ -542,15 +639,14 @@ static int collect_attr_files(
 	 */
 
 	if ((error = git_repository_item_path(&attrfile, repo, GIT_REPOSITORY_ITEM_INFO)) < 0 ||
-	    (error = push_attr_file(repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
-				    attrfile.ptr, GIT_ATTR_FILE_INREPO, true)) < 0) {
+	    (error = push_attr_file(repo, attr_session, files, attrfile.ptr, GIT_ATTR_FILE_INREPO)) < 0) {
 		if (error != GIT_ENOTFOUND)
 			goto cleanup;
 	}
 
 	info.repo = repo;
 	info.attr_session = attr_session;
-	info.flags = flags;
+	info.opts = opts;
 	info.workdir = workdir;
 	if (git_repository_index__weakptr(&info.index, repo) < 0)
 		git_error_clear(); /* no error even if there is no index */
@@ -565,18 +661,16 @@ static int collect_attr_files(
 		goto cleanup;
 
 	if (git_repository_attr_cache(repo)->cfg_attr_file != NULL) {
-		error = push_attr_file(repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
-				       NULL, git_repository_attr_cache(repo)->cfg_attr_file, true);
+		error = push_attr_file(repo, attr_session, files, NULL, git_repository_attr_cache(repo)->cfg_attr_file);
 		if (error < 0)
 			goto cleanup;
 	}
 
-	if ((flags & GIT_ATTR_CHECK_NO_SYSTEM) == 0) {
+	if (!opts || (opts->flags & GIT_ATTR_CHECK_NO_SYSTEM) == 0) {
 		error = system_attr_file(&dir, attr_session);
 
 		if (!error)
-			error = push_attr_file(repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
-					       NULL, dir.ptr, true);
+			error = push_attr_file(repo, attr_session, files, NULL, dir.ptr);
 		else if (error == GIT_ENOTFOUND)
 			error = 0;
 	}
diff --git a/src/attr_file.c b/src/attr_file.c
index 8269272..f862738 100644
--- a/src/attr_file.c
+++ b/src/attr_file.c
@@ -33,7 +33,7 @@ static void attr_file_free(git_attr_file *file)
 int git_attr_file__new(
 	git_attr_file **out,
 	git_attr_file_entry *entry,
-	git_attr_file_source source)
+	git_attr_file_source *source)
 {
 	git_attr_file *attrs = git__calloc(1, sizeof(git_attr_file));
 	GIT_ERROR_CHECK_ALLOC(attrs);
@@ -47,8 +47,8 @@ int git_attr_file__new(
 		goto on_error;
 
 	GIT_REFCOUNT_INC(attrs);
-	attrs->entry  = entry;
-	attrs->source = source;
+	attrs->entry = entry;
+	memcpy(&attrs->source, source, sizeof(git_attr_file_source));
 	*out = attrs;
 	return 0;
 
@@ -108,11 +108,12 @@ int git_attr_file__load(
 	git_repository *repo,
 	git_attr_session *attr_session,
 	git_attr_file_entry *entry,
-	git_attr_file_source source,
+	git_attr_file_source *source,
 	git_attr_file_parser parser,
 	bool allow_macros)
 {
 	int error = 0;
+	git_commit *commit = NULL;
 	git_tree *tree = NULL;
 	git_tree_entry *tree_entry = NULL;
 	git_blob *blob = NULL;
@@ -128,11 +129,11 @@ int git_attr_file__load(
 
 	*out = NULL;
 
-	switch (source) {
-	case GIT_ATTR_FILE__IN_MEMORY:
+	switch (source->type) {
+	case GIT_ATTR_FILE_SOURCE_MEMORY:
 		/* in-memory attribute file doesn't need data */
 		break;
-	case GIT_ATTR_FILE__FROM_INDEX: {
+	case GIT_ATTR_FILE_SOURCE_INDEX: {
 		if ((error = attr_file_oid_from_index(&id, repo, entry->path)) < 0 ||
 			(error = git_blob_lookup(&blob, repo, &id)) < 0)
 			return error;
@@ -145,7 +146,7 @@ int git_attr_file__load(
 		git_buf_put(&content, git_blob_rawcontent(blob), (size_t)blobsize);
 		break;
 	}
-	case GIT_ATTR_FILE__FROM_FILE: {
+	case GIT_ATTR_FILE_SOURCE_FILE: {
 		int fd = -1;
 
 		/* For open or read errors, pretend that we got ENOTFOUND. */
@@ -162,10 +163,31 @@ int git_attr_file__load(
 
 		break;
 	}
-	case GIT_ATTR_FILE__FROM_HEAD: {
-		if ((error = git_repository_head_tree(&tree, repo)) < 0 ||
-		    (error = git_tree_entry_bypath(&tree_entry, tree, entry->path)) < 0 ||
-		    (error = git_blob_lookup(&blob, repo, git_tree_entry_id(tree_entry))) < 0)
+	case GIT_ATTR_FILE_SOURCE_COMMIT: {
+		if (source->commit_id) {
+			if ((error = git_commit_lookup(&commit, repo, source->commit_id)) < 0 ||
+			    (error = git_commit_tree(&tree, commit)) < 0)
+				goto cleanup;
+		} else {
+			if ((error = git_repository_head_tree(&tree, repo)) < 0)
+				goto cleanup;
+		}
+
+		if ((error = git_tree_entry_bypath(&tree_entry, tree, entry->path)) < 0) {
+			/*
+			 * If the attributes file does not exist, we can
+			 * cache an empty file for this commit to prevent
+			 * needless future lookups.
+			 */
+			if (error == GIT_ENOTFOUND) {
+				error = 0;
+				break;
+			}
+
+			goto cleanup;
+		}
+
+		if ((error = git_blob_lookup(&blob, repo, git_tree_entry_id(tree_entry))) < 0)
 			goto cleanup;
 
 		/*
@@ -182,7 +204,7 @@ int git_attr_file__load(
 		break;
 	}
 	default:
-		git_error_set(GIT_ERROR_INVALID, "unknown file source %d", source);
+		git_error_set(GIT_ERROR_INVALID, "unknown file source %d", source->type);
 		return -1;
 	}
 
@@ -210,11 +232,11 @@ int git_attr_file__load(
 	/* write cache breakers */
 	if (nonexistent)
 		file->nonexistent = 1;
-	else if (source == GIT_ATTR_FILE__FROM_INDEX)
+	else if (source->type == GIT_ATTR_FILE_SOURCE_INDEX)
 		git_oid_cpy(&file->cache_data.oid, git_blob_id(blob));
-	else if (source == GIT_ATTR_FILE__FROM_HEAD)
+	else if (source->type == GIT_ATTR_FILE_SOURCE_COMMIT)
 		git_oid_cpy(&file->cache_data.oid, git_tree_id(tree));
-	else if (source == GIT_ATTR_FILE__FROM_FILE)
+	else if (source->type == GIT_ATTR_FILE_SOURCE_FILE)
 		git_futils_filestamp_set_from_stat(&file->cache_data.stamp, &st);
 	/* else always cacheable */
 
@@ -224,6 +246,7 @@ cleanup:
 	git_blob_free(blob);
 	git_tree_entry_free(tree_entry);
 	git_tree_free(tree);
+	git_commit_free(commit);
 	git_buf_dispose(&content);
 
 	return error;
@@ -232,7 +255,8 @@ cleanup:
 int git_attr_file__out_of_date(
 	git_repository *repo,
 	git_attr_session *attr_session,
-	git_attr_file *file)
+	git_attr_file *file,
+	git_attr_file_source *source)
 {
 	if (!file)
 		return 1;
@@ -245,15 +269,15 @@ int git_attr_file__out_of_date(
 	else if (file->nonexistent)
 		return 1;
 
-	switch (file->source) {
-	case GIT_ATTR_FILE__IN_MEMORY:
+	switch (file->source.type) {
+	case GIT_ATTR_FILE_SOURCE_MEMORY:
 		return 0;
 
-	case GIT_ATTR_FILE__FROM_FILE:
+	case GIT_ATTR_FILE_SOURCE_FILE:
 		return git_futils_filestamp_check(
 			&file->cache_data.stamp, file->entry->fullpath);
 
-	case GIT_ATTR_FILE__FROM_INDEX: {
+	case GIT_ATTR_FILE_SOURCE_INDEX: {
 		int error;
 		git_oid id;
 
@@ -264,21 +288,34 @@ int git_attr_file__out_of_date(
 		return (git_oid__cmp(&file->cache_data.oid, &id) != 0);
 	}
 
-	case GIT_ATTR_FILE__FROM_HEAD: {
-		git_tree *tree;
+	case GIT_ATTR_FILE_SOURCE_COMMIT: {
+		git_tree *tree = NULL;
 		int error;
 
-		if ((error = git_repository_head_tree(&tree, repo)) < 0)
+		if (source->commit_id) {
+			git_commit *commit = NULL;
+
+			if ((error = git_commit_lookup(&commit, repo, source->commit_id)) < 0)
+				return error;
+
+			error = git_commit_tree(&tree, commit);
+
+			git_commit_free(commit);
+		} else {
+			error = git_repository_head_tree(&tree, repo);
+		}
+
+		if (error < 0)
 			return error;
 
-		error = git_oid__cmp(&file->cache_data.oid, git_tree_id(tree));
+		error = (git_oid__cmp(&file->cache_data.oid, git_tree_id(tree)) != 0);
 
 		git_tree_free(tree);
 		return error;
 	}
 
 	default:
-		git_error_set(GIT_ERROR_INVALID, "invalid file type %d", file->source);
+		git_error_set(GIT_ERROR_INVALID, "invalid file type %d", file->source.type);
 		return -1;
 	}
 }
@@ -389,6 +426,7 @@ int git_attr_file__lookup_one(
 int git_attr_file__load_standalone(git_attr_file **out, const char *path)
 {
 	git_buf content = GIT_BUF_INIT;
+	git_attr_file_source source = { GIT_ATTR_FILE_SOURCE_FILE };
 	git_attr_file *file = NULL;
 	int error;
 
@@ -400,7 +438,7 @@ int git_attr_file__load_standalone(git_attr_file **out, const char *path)
 	 * don't have to free it - freeing file+pool will free cache entry, too.
 	 */
 
-	if ((error = git_attr_file__new(&file, NULL, GIT_ATTR_FILE__FROM_FILE)) < 0 ||
+	if ((error = git_attr_file__new(&file, NULL, &source)) < 0 ||
 	    (error = git_attr_file__parse_buffer(NULL, file, content.ptr, true)) < 0 ||
 	    (error = git_attr_cache__alloc_file_entry(&file->entry, NULL, NULL, path, &file->pool)) < 0)
 		goto out;
diff --git a/src/attr_file.h b/src/attr_file.h
index 617436b..16e33ca 100644
--- a/src/attr_file.h
+++ b/src/attr_file.h
@@ -37,12 +37,30 @@
 	(GIT_ATTR_FNMATCH_ALLOWSPACE | GIT_ATTR_FNMATCH_ALLOWNEG | GIT_ATTR_FNMATCH_ALLOWMACRO)
 
 typedef enum {
-	GIT_ATTR_FILE__IN_MEMORY   = 0,
-	GIT_ATTR_FILE__FROM_FILE   = 1,
-	GIT_ATTR_FILE__FROM_INDEX  = 2,
-	GIT_ATTR_FILE__FROM_HEAD   = 3,
+	GIT_ATTR_FILE_SOURCE_MEMORY = 0,
+	GIT_ATTR_FILE_SOURCE_FILE   = 1,
+	GIT_ATTR_FILE_SOURCE_INDEX  = 2,
+	GIT_ATTR_FILE_SOURCE_COMMIT = 3,
 
-	GIT_ATTR_FILE_NUM_SOURCES  = 4
+	GIT_ATTR_FILE_NUM_SOURCES   = 4
+} git_attr_file_source_t;
+
+typedef struct {
+	/* The source location for the attribute file. */
+	git_attr_file_source_t type;
+
+	/*
+	 * The filename of the attribute file to read (relative to the
+	 * given base path).
+	 */
+	const char *base;
+	const char *filename;
+
+	/*
+	 * The commit ID when the given source type is a commit (or NULL
+	 * for the repository's HEAD commit.)
+	 */
+	git_oid *commit_id;
 } git_attr_file_source;
 
 extern const char *git_attr__true;
@@ -124,7 +142,7 @@ extern int git_attr_get_many_with_session(
 	const char **values_out,
 	git_repository *repo,
 	git_attr_session *attr_session,
-	uint32_t flags,
+	git_attr_options *opts,
 	const char *path,
 	size_t num_attr,
 	const char **names);
@@ -142,7 +160,7 @@ typedef int (*git_attr_file_parser)(
 int git_attr_file__new(
 	git_attr_file **out,
 	git_attr_file_entry *entry,
-	git_attr_file_source source);
+	git_attr_file_source *source);
 
 void git_attr_file__free(git_attr_file *file);
 
@@ -151,7 +169,7 @@ int git_attr_file__load(
 	git_repository *repo,
 	git_attr_session *attr_session,
 	git_attr_file_entry *ce,
-	git_attr_file_source source,
+	git_attr_file_source *source,
 	git_attr_file_parser parser,
 	bool allow_macros);
 
@@ -159,7 +177,7 @@ int git_attr_file__load_standalone(
 	git_attr_file **out, const char *path);
 
 int git_attr_file__out_of_date(
-	git_repository *repo, git_attr_session *session, git_attr_file *file);
+	git_repository *repo, git_attr_session *session, git_attr_file *file, git_attr_file_source *source);
 
 int git_attr_file__parse_buffer(
 	git_repository *repo, git_attr_file *attrs, const char *data, bool allow_macros);
diff --git a/src/attrcache.c b/src/attrcache.c
index 32513da..7fe2bfb 100644
--- a/src/attrcache.c
+++ b/src/attrcache.c
@@ -112,7 +112,7 @@ static int attr_cache_upsert(git_attr_cache *cache, git_attr_file *file)
 	 * Replace the existing value if another thread has
 	 * created it in the meantime.
 	 */
-	old = git_atomic_swap(entry->file[file->source], file);
+	old = git_atomic_swap(entry->file[file->source.type], file);
 
 	if (old) {
 		GIT_REFCOUNT_OWN(old, NULL);
@@ -136,7 +136,7 @@ static int attr_cache_remove(git_attr_cache *cache, git_attr_file *file)
 		return error;
 
 	if ((entry = attr_cache_lookup_entry(cache, file->entry->path)) != NULL)
-		old = git_atomic_compare_and_swap(&entry->file[file->source], file, NULL);
+		old = git_atomic_compare_and_swap(&entry->file[file->source.type], file, NULL);
 
 	attr_cache_unlock(cache);
 
@@ -158,41 +158,42 @@ static int attr_cache_lookup(
 	git_attr_file_entry **out_entry,
 	git_repository *repo,
 	git_attr_session *attr_session,
-	git_attr_file_source source,
-	const char *base,
-	const char *filename)
+	git_attr_file_source *source)
 {
 	int error = 0;
 	git_buf path = GIT_BUF_INIT;
-	const char *wd = git_repository_workdir(repo), *relfile;
+	const char *wd = git_repository_workdir(repo);
+	const char *filename;
 	git_attr_cache *cache = git_repository_attr_cache(repo);
 	git_attr_file_entry *entry = NULL;
 	git_attr_file *file = NULL;
 
 	/* join base and path as needed */
-	if (base != NULL && git_path_root(filename) < 0) {
+	if (source->base != NULL && git_path_root(source->filename) < 0) {
 		git_buf *p = attr_session ? &attr_session->tmp : &path;
 
-		if (git_buf_joinpath(p, base, filename) < 0 ||
+		if (git_buf_joinpath(p, source->base, source->filename) < 0 ||
 		    git_path_validate_workdir_buf(repo, p) < 0)
 			return -1;
 
 		filename = p->ptr;
+	} else {
+		filename = source->filename;
 	}
 
-	relfile = filename;
-	if (wd && !git__prefixcmp(relfile, wd))
-		relfile += strlen(wd);
+	if (wd && !git__prefixcmp(filename, wd))
+		filename += strlen(wd);
 
 	/* check cache for existing entry */
 	if ((error = attr_cache_lock(cache)) < 0)
 		goto cleanup;
 
-	entry = attr_cache_lookup_entry(cache, relfile);
-	if (!entry)
-		error = attr_cache_make_entry(&entry, repo, relfile);
-	else if (entry->file[source] != NULL) {
-		file = entry->file[source];
+	entry = attr_cache_lookup_entry(cache, filename);
+
+	if (!entry) {
+		error = attr_cache_make_entry(&entry, repo, filename);
+	} else if (entry->file[source->type] != NULL) {
+		file = entry->file[source->type];
 		GIT_REFCOUNT_INC(file);
 	}
 
@@ -210,9 +211,7 @@ int git_attr_cache__get(
 	git_attr_file **out,
 	git_repository *repo,
 	git_attr_session *attr_session,
-	git_attr_file_source source,
-	const char *base,
-	const char *filename,
+	git_attr_file_source *source,
 	git_attr_file_parser parser,
 	bool allow_macros)
 {
@@ -221,19 +220,21 @@ int git_attr_cache__get(
 	git_attr_file_entry *entry = NULL;
 	git_attr_file *file = NULL, *updated = NULL;
 
-	if ((error = attr_cache_lookup(
-			&file, &entry, repo, attr_session, source, base, filename)) < 0)
+	if ((error = attr_cache_lookup(&file, &entry, repo, attr_session, source)) < 0)
 		return error;
 
 	/* load file if we don't have one or if existing one is out of date */
-	if (!file || (error = git_attr_file__out_of_date(repo, attr_session, file)) > 0)
-		error = git_attr_file__load(&updated, repo, attr_session, entry, source, parser, allow_macros);
+	if (!file ||
+	    (error = git_attr_file__out_of_date(repo, attr_session, file, source)) > 0)
+		error = git_attr_file__load(&updated, repo, attr_session,
+		                            entry, source, parser,
+		                            allow_macros);
 
 	/* if we loaded the file, insert into and/or update cache */
 	if (updated) {
-		if ((error = attr_cache_upsert(cache, updated)) < 0)
+		if ((error = attr_cache_upsert(cache, updated)) < 0) {
 			git_attr_file__free(updated);
-		else {
+		} else {
 			git_attr_file__free(file); /* offset incref from lookup */
 			file = updated;
 		}
@@ -260,7 +261,7 @@ int git_attr_cache__get(
 
 bool git_attr_cache__is_cached(
 	git_repository *repo,
-	git_attr_file_source source,
+	git_attr_file_source_t source_type,
 	const char *filename)
 {
 	git_attr_cache *cache = git_repository_attr_cache(repo);
@@ -273,7 +274,7 @@ bool git_attr_cache__is_cached(
 	if ((entry = git_strmap_get(files, filename)) == NULL)
 		return false;
 
-	return entry && (entry->file[source] != NULL);
+	return entry && (entry->file[source_type] != NULL);
 }
 
 
diff --git a/src/attrcache.h b/src/attrcache.h
index 5e2fb29..b13e0e8 100644
--- a/src/attrcache.h
+++ b/src/attrcache.h
@@ -31,16 +31,14 @@ extern int git_attr_cache__get(
 	git_attr_file **file,
 	git_repository *repo,
 	git_attr_session *attr_session,
-	git_attr_file_source source,
-	const char *base,
-	const char *filename,
+	git_attr_file_source *source,
 	git_attr_file_parser parser,
 	bool allow_macros);
 
 extern bool git_attr_cache__is_cached(
 	git_repository *repo,
-	git_attr_file_source source,
-	const char *path);
+	git_attr_file_source_t source_type,
+	const char *filename);
 
 extern int git_attr_cache__alloc_file_entry(
 	git_attr_file_entry **out,
diff --git a/src/blob.c b/src/blob.c
index 169e345..01ebf07 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -421,7 +421,7 @@ int git_blob_filter(
 	int error = 0;
 	git_filter_list *fl = NULL;
 	git_blob_filter_options opts = GIT_BLOB_FILTER_OPTIONS_INIT;
-	git_filter_flag_t flags = GIT_FILTER_DEFAULT;
+	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
 
 	GIT_ASSERT_ARG(blob);
 	GIT_ASSERT_ARG(path);
@@ -441,14 +441,19 @@ int git_blob_filter(
 		return 0;
 
 	if ((opts.flags & GIT_BLOB_FILTER_NO_SYSTEM_ATTRIBUTES) != 0)
-		flags |= GIT_FILTER_NO_SYSTEM_ATTRIBUTES;
+		filter_opts.flags |= GIT_FILTER_NO_SYSTEM_ATTRIBUTES;
 
 	if ((opts.flags & GIT_BLOB_FILTER_ATTRIBUTES_FROM_HEAD) != 0)
-		flags |= GIT_FILTER_ATTRIBUTES_FROM_HEAD;
+		filter_opts.flags |= GIT_FILTER_ATTRIBUTES_FROM_HEAD;
 
-	if (!(error = git_filter_list_load(
+	if ((opts.flags & GIT_BLOB_FILTER_ATTRIBUTES_FROM_COMMIT) != 0) {
+		filter_opts.flags |= GIT_FILTER_ATTRIBUTES_FROM_COMMIT;
+		filter_opts.commit_id = opts.commit_id;
+	}
+
+	if (!(error = git_filter_list_load_ext(
 			&fl, git_blob_owner(blob), blob, path,
-			GIT_FILTER_TO_WORKTREE, flags))) {
+			GIT_FILTER_TO_WORKTREE, &filter_opts))) {
 
 		error = git_filter_list_apply_to_blob(out, fl, blob);
 
diff --git a/src/checkout.c b/src/checkout.c
index 2f84df7..31d473e 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -1513,7 +1513,7 @@ static int blob_content_to_file(
 	int flags = data->opts.file_open_flags;
 	mode_t file_mode = data->opts.file_mode ?
 		data->opts.file_mode : entry_filemode;
-	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
+	git_filter_session filter_session = GIT_FILTER_SESSION_INIT;
 	struct checkout_stream writer;
 	mode_t mode;
 	git_filter_list *fl = NULL;
@@ -1536,13 +1536,13 @@ static int blob_content_to_file(
 		return fd;
 	}
 
-	filter_opts.attr_session = &data->attr_session;
-	filter_opts.temp_buf = &data->tmp;
+	filter_session.attr_session = &data->attr_session;
+	filter_session.temp_buf = &data->tmp;
 
 	if (!data->opts.disable_filters &&
-		(error = git_filter_list__load_ext(
+		(error = git_filter_list__load(
 			&fl, data->repo, blob, hint_path,
-			GIT_FILTER_TO_WORKTREE, &filter_opts))) {
+			GIT_FILTER_TO_WORKTREE, &filter_session))) {
 		p_close(fd);
 		return error;
 	}
@@ -2064,7 +2064,7 @@ static int checkout_write_merge(
 	git_merge_file_result result = {0};
 	git_filebuf output = GIT_FILEBUF_INIT;
 	git_filter_list *fl = NULL;
-	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
+	git_filter_session filter_session = GIT_FILTER_SESSION_INIT;
 	int error = 0;
 
 	if (data->opts.checkout_strategy & GIT_CHECKOUT_CONFLICT_STYLE_DIFF3)
@@ -2114,12 +2114,12 @@ static int checkout_write_merge(
 		in_data.ptr = (char *)result.ptr;
 		in_data.size = result.len;
 
-		filter_opts.attr_session = &data->attr_session;
-		filter_opts.temp_buf = &data->tmp;
+		filter_session.attr_session = &data->attr_session;
+		filter_session.temp_buf = &data->tmp;
 
-		if ((error = git_filter_list__load_ext(
+		if ((error = git_filter_list__load(
 				&fl, data->repo, NULL, git_buf_cstr(&path_workdir),
-				GIT_FILTER_TO_WORKTREE, &filter_opts)) < 0 ||
+				GIT_FILTER_TO_WORKTREE, &filter_session)) < 0 ||
 			(error = git_filter_list__convert_buf(&out_data, fl, &in_data)) < 0)
 			goto done;
 	} else {
diff --git a/src/filter.c b/src/filter.c
index 6c09a6a..eed175e 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -19,12 +19,12 @@
 #include "array.h"
 
 struct git_filter_source {
-	git_repository *repo;
-	const char     *path;
-	git_oid         oid;  /* zero if unknown (which is likely) */
-	uint16_t        filemode; /* zero if unknown */
-	git_filter_mode_t mode;
-	uint32_t        flags;
+	git_repository    *repo;
+	const char        *path;
+	git_oid            oid;  /* zero if unknown (which is likely) */
+	uint16_t           filemode; /* zero if unknown */
+	git_filter_mode_t  mode;
+	git_filter_options options;
 };
 
 typedef struct {
@@ -396,7 +396,7 @@ git_filter_mode_t git_filter_source_mode(const git_filter_source *src)
 
 uint32_t git_filter_source_flags(const git_filter_source *src)
 {
-	return src->flags;
+	return src->options.flags;
 }
 
 static int filter_list_new(
@@ -416,7 +416,8 @@ static int filter_list_new(
 	fl->source.repo = src->repo;
 	fl->source.path = fl->path;
 	fl->source.mode = src->mode;
-	fl->source.flags = src->flags;
+
+	memcpy(&fl->source.options, &src->options, sizeof(git_filter_options));
 
 	*out = fl;
 	return 0;
@@ -425,25 +426,30 @@ static int filter_list_new(
 static int filter_list_check_attributes(
 	const char ***out,
 	git_repository *repo,
-	git_attr_session *attr_session,
+	git_filter_session *filter_session,
 	git_filter_def *fdef,
 	const git_filter_source *src)
 {
 	const char **strs = git__calloc(fdef->nattrs, sizeof(const char *));
-	uint32_t flags = 0;
+	git_attr_options attr_opts = GIT_ATTR_OPTIONS_INIT;
 	size_t i;
 	int error;
 
 	GIT_ERROR_CHECK_ALLOC(strs);
 
-	if ((src->flags & GIT_FILTER_NO_SYSTEM_ATTRIBUTES) != 0)
-		flags |= GIT_ATTR_CHECK_NO_SYSTEM;
+	if ((src->options.flags & GIT_FILTER_NO_SYSTEM_ATTRIBUTES) != 0)
+		attr_opts.flags |= GIT_ATTR_CHECK_NO_SYSTEM;
+
+	if ((src->options.flags & GIT_FILTER_ATTRIBUTES_FROM_HEAD) != 0)
+		attr_opts.flags |= GIT_ATTR_CHECK_INCLUDE_HEAD;
 
-	if ((src->flags & GIT_FILTER_ATTRIBUTES_FROM_HEAD) != 0)
-		flags |= GIT_ATTR_CHECK_INCLUDE_HEAD;
+	if ((src->options.flags & GIT_FILTER_ATTRIBUTES_FROM_COMMIT) != 0) {
+		attr_opts.flags |= GIT_ATTR_CHECK_INCLUDE_COMMIT;
+		attr_opts.commit_id = src->options.commit_id;
+	}
 
 	error = git_attr_get_many_with_session(
-		strs, repo, attr_session, flags, src->path, fdef->nattrs, fdef->attrs);
+		strs, repo, filter_session->attr_session, &attr_opts, src->path, fdef->nattrs, fdef->attrs);
 
 	/* if no values were found but no matches are needed, it's okay! */
 	if (error == GIT_ENOTFOUND && !fdef->nmatches) {
@@ -488,17 +494,17 @@ int git_filter_list_new(
 	src.repo = repo;
 	src.path = NULL;
 	src.mode = mode;
-	src.flags = flags;
+	src.options.flags = flags;
 	return filter_list_new(out, &src);
 }
 
-int git_filter_list__load_ext(
+int git_filter_list__load(
 	git_filter_list **filters,
 	git_repository *repo,
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	git_filter_options *filter_opts)
+	git_filter_session *filter_session)
 {
 	int error = 0;
 	git_filter_list *fl = NULL;
@@ -515,7 +521,8 @@ int git_filter_list__load_ext(
 	src.repo = repo;
 	src.path = path;
 	src.mode = mode;
-	src.flags = filter_opts->flags;
+
+	memcpy(&src.options, &filter_session->options, sizeof(git_filter_options));
 
 	if (blob)
 		git_oid_cpy(&src.oid, git_blob_id(blob));
@@ -529,7 +536,8 @@ int git_filter_list__load_ext(
 
 		if (fdef->nattrs > 0) {
 			error = filter_list_check_attributes(
-				&values, repo, filter_opts->attr_session, fdef, &src);
+				&values, repo,
+				filter_session, fdef, &src);
 
 			if (error == GIT_ENOTFOUND) {
 				error = 0;
@@ -556,7 +564,7 @@ int git_filter_list__load_ext(
 				if ((error = filter_list_new(&fl, &src)) < 0)
 					break;
 
-				fl->temp_buf = filter_opts->temp_buf;
+				fl->temp_buf = filter_session->temp_buf;
 			}
 
 			fe = git_array_alloc(fl->filters);
@@ -580,6 +588,23 @@ int git_filter_list__load_ext(
 	return error;
 }
 
+int git_filter_list_load_ext(
+	git_filter_list **filters,
+	git_repository *repo,
+	git_blob *blob, /* can be NULL */
+	const char *path,
+	git_filter_mode_t mode,
+	git_filter_options *opts)
+{
+	git_filter_session filter_session = GIT_FILTER_SESSION_INIT;
+
+	if (opts)
+		memcpy(&filter_session.options, opts, sizeof(git_filter_options));
+
+	return git_filter_list__load(
+		filters, repo, blob, path, mode, &filter_session);
+}
+
 int git_filter_list_load(
 	git_filter_list **filters,
 	git_repository *repo,
@@ -588,12 +613,12 @@ int git_filter_list_load(
 	git_filter_mode_t mode,
 	uint32_t flags)
 {
-	git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
+	git_filter_session filter_session = GIT_FILTER_SESSION_INIT;
 
-	filter_opts.flags = flags;
+	filter_session.options.flags = flags;
 
-	return git_filter_list__load_ext(
-		filters, repo, blob, path, mode, &filter_opts);
+	return git_filter_list__load(
+		filters, repo, blob, path, mode, &filter_session);
 }
 
 void git_filter_list_free(git_filter_list *fl)
diff --git a/src/filter.h b/src/filter.h
index bbc4c0f..55ed50e 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -16,24 +16,24 @@
 #define GIT_FILTER_BYTES_TO_CHECK_NUL 8000
 
 typedef struct {
+	git_filter_options options;
 	git_attr_session *attr_session;
 	git_buf *temp_buf;
-	uint32_t flags;
-} git_filter_options;
+} git_filter_session;
 
-#define GIT_FILTER_OPTIONS_INIT {0}
+#define GIT_FILTER_SESSION_INIT {GIT_FILTER_OPTIONS_INIT, 0}
 
 extern int git_filter_global_init(void);
 
 extern void git_filter_free(git_filter *filter);
 
-extern int git_filter_list__load_ext(
+extern int git_filter_list__load(
 	git_filter_list **filters,
 	git_repository *repo,
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
-	git_filter_options *filter_opts);
+	git_filter_session *filter_session);
 
 /*
  * The given input buffer will be converted to the given output buffer.
diff --git a/src/ignore.c b/src/ignore.c
index 948c58d..f7551cd 100644
--- a/src/ignore.c
+++ b/src/ignore.c
@@ -247,11 +247,12 @@ static int push_ignore_file(
 	const char *base,
 	const char *filename)
 {
-	int error = 0;
+	git_attr_file_source source = { GIT_ATTR_FILE_SOURCE_FILE, base, filename };
 	git_attr_file *file = NULL;
+	int error = 0;
+
+	error = git_attr_cache__get(&file, ignores->repo, NULL, &source, parse_ignore_file, false);
 
-	error = git_attr_cache__get(&file, ignores->repo, NULL, GIT_ATTR_FILE__FROM_FILE,
-				    base, filename, parse_ignore_file, false);
 	if (error < 0)
 		return error;
 
@@ -272,13 +273,13 @@ static int push_one_ignore(void *payload, const char *path)
 
 static int get_internal_ignores(git_attr_file **out, git_repository *repo)
 {
+	git_attr_file_source source = { GIT_ATTR_FILE_SOURCE_MEMORY, NULL, GIT_IGNORE_INTERNAL };
 	int error;
 
 	if ((error = git_attr_cache__init(repo)) < 0)
 		return error;
 
-	error = git_attr_cache__get(out, repo, NULL, GIT_ATTR_FILE__IN_MEMORY, NULL,
-				    GIT_IGNORE_INTERNAL, NULL, false);
+	error = git_attr_cache__get(out, repo, NULL, &source, NULL, false);
 
 	/* if internal rules list is empty, insert default rules */
 	if (!error && !(*out)->rules.length)
diff --git a/tests/attr/lookup.c b/tests/attr/lookup.c
index 29a66b0..bfb2e87 100644
--- a/tests/attr/lookup.c
+++ b/tests/attr/lookup.c
@@ -236,6 +236,7 @@ void test_attr_lookup__check_attr_examples(void)
 void test_attr_lookup__from_buffer(void)
 {
 	git_attr_file *file;
+	git_attr_file_source source = {0};
 
 	struct attr_expected cases[] = {
 		{ "abc", "foo", EXPECT_TRUE, NULL },
@@ -250,7 +251,7 @@ void test_attr_lookup__from_buffer(void)
 		{ NULL, NULL, 0, NULL }
 	};
 
-	cl_git_pass(git_attr_file__new(&file, NULL, 0));
+	cl_git_pass(git_attr_file__new(&file, NULL, &source));
 
 	cl_git_pass(git_attr_file__parse_buffer(NULL, file, "a* foo\nabc bar\n* baz", true));
 
diff --git a/tests/attr/repo.c b/tests/attr/repo.c
index 36beeb0..eabc033 100644
--- a/tests/attr/repo.c
+++ b/tests/attr/repo.c
@@ -71,11 +71,11 @@ void test_attr_repo__get_one(void)
 	}
 
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".git/info/attributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".git/info/attributes"));
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".gitattributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".gitattributes"));
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, "sub/.gitattributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, "sub/.gitattributes"));
 }
 
 void test_attr_repo__get_one_start_deep(void)
@@ -92,11 +92,11 @@ void test_attr_repo__get_one_start_deep(void)
 	}
 
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".git/info/attributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".git/info/attributes"));
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".gitattributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".gitattributes"));
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, "sub/.gitattributes"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, "sub/.gitattributes"));
 }
 
 void test_attr_repo__get_many(void)
@@ -341,7 +341,7 @@ void test_attr_repo__sysdir_with_session(void)
 	g_repo = cl_git_sandbox_reopen();
 
 	cl_git_pass(git_attr_session__init(&session, g_repo));
-	cl_git_pass(git_attr_get_many_with_session(values, g_repo, &session, 0, "file", ARRAY_SIZE(attrs), attrs));
+	cl_git_pass(git_attr_get_many_with_session(values, g_repo, &session, NULL, "file", ARRAY_SIZE(attrs), attrs));
 
 	cl_assert_equal_s(values[0], "1");
 	cl_assert_equal_s(values[1], "2");
diff --git a/tests/filter/bare.c b/tests/filter/bare.c
index 7319b52..f8e3423 100644
--- a/tests/filter/bare.c
+++ b/tests/filter/bare.c
@@ -132,3 +132,63 @@ void test_filter_bare__sanitizes(void)
 	git_blob_free(blob);
 }
 
+void test_filter_bare__from_specific_commit_one(void)
+{
+	git_blob_filter_options opts = GIT_BLOB_FILTER_OPTIONS_INIT;
+	git_blob *blob;
+	git_buf buf = { 0 };
+	git_oid commit_id;
+
+	cl_git_pass(git_oid_fromstr(&commit_id, "b8986fec0f7bde90f78ac72706e782d82f24f2f0"));
+
+	opts.flags |= GIT_BLOB_FILTER_NO_SYSTEM_ATTRIBUTES;
+	opts.flags |= GIT_BLOB_FILTER_ATTRIBUTES_FROM_COMMIT;
+	opts.commit_id = &commit_id;
+
+	cl_git_pass(git_revparse_single(
+		(git_object **)&blob, g_repo, "055c872")); /* ident */
+
+	cl_assert_equal_s("$Id$\n", git_blob_rawcontent(blob));
+
+	cl_git_pass(git_blob_filter(&buf, blob, "ident.bin", &opts));
+	cl_assert_equal_s("$Id$\n", buf.ptr);
+
+	cl_git_pass(git_blob_filter(&buf, blob, "ident.identlf", &opts));
+	cl_assert_equal_s("$Id: 055c8729cdcc372500a08db659c045e16c4409fb $\n", buf.ptr);
+
+	git_buf_dispose(&buf);
+	git_blob_free(blob);
+}
+
+void test_filter_bare__from_specific_commit_with_no_attributes_file(void)
+{
+	git_blob_filter_options opts = GIT_BLOB_FILTER_OPTIONS_INIT;
+	git_blob *blob;
+	git_buf buf = { 0 };
+	git_oid commit_id;
+
+	cl_git_pass(git_oid_fromstr(&commit_id, "5afb6a14a864e30787857dd92af837e8cdd2cb1b"));
+
+	opts.flags |= GIT_BLOB_FILTER_NO_SYSTEM_ATTRIBUTES;
+	opts.flags |= GIT_BLOB_FILTER_ATTRIBUTES_FROM_COMMIT;
+	opts.commit_id = &commit_id;
+
+	cl_git_pass(git_revparse_single(
+		(git_object **)&blob, g_repo, "799770d")); /* all-lf */
+
+	cl_assert_equal_s(ALL_LF_TEXT_RAW, git_blob_rawcontent(blob));
+
+	cl_git_pass(git_blob_filter(&buf, blob, "file.bin", &opts));
+	cl_assert_equal_s(ALL_LF_TEXT_RAW, buf.ptr);
+
+	/* we never convert CRLF -> LF on platforms that have LF */
+	cl_git_pass(git_blob_filter(&buf, blob, "file.lf", &opts));
+	cl_assert_equal_s(ALL_LF_TEXT_RAW, buf.ptr);
+
+	/* we never convert CRLF -> LF on platforms that have LF */
+	cl_git_pass(git_blob_filter(&buf, blob, "file.crlf", &opts));
+	cl_assert_equal_s(ALL_LF_TEXT_RAW, buf.ptr);
+
+	git_buf_dispose(&buf);
+	git_blob_free(blob);
+}
diff --git a/tests/ignore/status.c b/tests/ignore/status.c
index 188fbe4..83e821b 100644
--- a/tests/ignore/status.c
+++ b/tests/ignore/status.c
@@ -70,9 +70,9 @@ void test_ignore_status__0(void)
 
 	/* confirm that ignore files were cached */
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".git/info/exclude"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".git/info/exclude"));
 	cl_assert(git_attr_cache__is_cached(
-		g_repo, GIT_ATTR_FILE__FROM_FILE, ".gitignore"));
+		g_repo, GIT_ATTR_FILE_SOURCE_FILE, ".gitignore"));
 }
 
 
diff --git a/tests/resources/crlf.git/objects/05/5c8729cdcc372500a08db659c045e16c4409fb b/tests/resources/crlf.git/objects/05/5c8729cdcc372500a08db659c045e16c4409fb
new file mode 100644
index 0000000..44076ca
Binary files /dev/null and b/tests/resources/crlf.git/objects/05/5c8729cdcc372500a08db659c045e16c4409fb differ
diff --git a/tests/resources/crlf.git/objects/1e/c507638b806aba45d6142082885f2a9e88322d b/tests/resources/crlf.git/objects/1e/c507638b806aba45d6142082885f2a9e88322d
new file mode 100644
index 0000000..ca97967
Binary files /dev/null and b/tests/resources/crlf.git/objects/1e/c507638b806aba45d6142082885f2a9e88322d differ
diff --git a/tests/resources/crlf.git/objects/44/b0be18671a284f1156117b6338edac2663341c b/tests/resources/crlf.git/objects/44/b0be18671a284f1156117b6338edac2663341c
new file mode 100644
index 0000000..0576e62
Binary files /dev/null and b/tests/resources/crlf.git/objects/44/b0be18671a284f1156117b6338edac2663341c differ
diff --git a/tests/resources/crlf.git/objects/55/1b8fce462bba005ab6d34a2244d8a3f6b03dd0 b/tests/resources/crlf.git/objects/55/1b8fce462bba005ab6d34a2244d8a3f6b03dd0
new file mode 100644
index 0000000..7501c88
Binary files /dev/null and b/tests/resources/crlf.git/objects/55/1b8fce462bba005ab6d34a2244d8a3f6b03dd0 differ
diff --git a/tests/resources/crlf.git/objects/b8/986fec0f7bde90f78ac72706e782d82f24f2f0 b/tests/resources/crlf.git/objects/b8/986fec0f7bde90f78ac72706e782d82f24f2f0
new file mode 100644
index 0000000..d745d20
--- /dev/null
+++ b/tests/resources/crlf.git/objects/b8/986fec0f7bde90f78ac72706e782d82f24f2f0
@@ -0,0 +1,3 @@
+x
��M
+�0�]�s
%3�Dt�
��$�b�6�F��Q�����2Mc�nSWU`�6*��C��ĽG�w��,�|S��,��\
�����#��Y��
8t�);
q��ȳ��
+���5��V�G��-���~��ۥ2
=�`��ֲ���ml�?1�3�cn�
�H�]a�j�@�U
\ No newline at end of file
diff --git a/tests/resources/crlf.git/refs/heads/ident b/tests/resources/crlf.git/refs/heads/ident
new file mode 100644
index 0000000..8732f0c
--- /dev/null
+++ b/tests/resources/crlf.git/refs/heads/ident
@@ -0,0 +1 @@
+b8986fec0f7bde90f78ac72706e782d82f24f2f0
diff --git a/tests/resources/crlf.git/refs/heads/no-ident b/tests/resources/crlf.git/refs/heads/no-ident
new file mode 100644
index 0000000..fa9a673
--- /dev/null
+++ b/tests/resources/crlf.git/refs/heads/no-ident
@@ -0,0 +1 @@
+1ec507638b806aba45d6142082885f2a9e88322d